Css > Cross Site Scripting

This is an article on Css > Cross Site Scripting in Ethical hacking Tips.

I will be explaining in brief some things about it.

"What is Cross Site Scripting?"

Cross site scripting (also known as XSS) occurs when a web application gathers malicious data from a user. The data is usually gathered in the form of a hyperlink which contains malicious content within it. The user will most likely click on this link from another website, instant message, or simply just reading a web board or email message. Usually the attacker will encode the malicious portion of the link to the site in HEX (or other encoding methods) so the request is less suspicious looking to the user when clicked on. After the data is collected by the web application, it creates an output page for the user containing the malicious data that was originally sent to it, but in a manner to make it appear as valid content from the website. Many popular guestbook and forum programs allow users to submit posts with html and javascript embedded in them. If for example I was logged in as "john" and read a message by "joe" that contained malicious javascript in it, then it may be possible for "joe" to hijack my session just by reading his bulletin board post. Further details on how attacks like this are accomplished via "cookie theft" are explained in detail below.

"What does XSS and CSS mean?"

Often people refer to Cross Site Scripting as CSS. There has been a lot of confusion with Cascading Style Sheets (CSS) and cross site scripting. Some security people refer to Cross Site Scripting as XSS. If you hear someone say "I found a XSS hole", they are talking about Cross Site Scripting for certain.

"What are the threats of Cross Site Scripting?"

Often attackers will inject JavaScript, VBScript, ActiveX, HTML, or Flash into a vulnerable application to fool a user (Read below for further details) in order to gather data from them. Everything from account hijacking, changing of user settings, cookie theft/poisoning, or false advertising is possible. New malicious uses are being found every day for XSS attacks. The post below by Brett Moore brings up a good point with regard to "Denial Of Service", and potential "auto-attacking" of hosts if a user simply reads a post on a message board.

"What are some examples of cross site scripting attacks?"

One product with many XSS holes is the popular PHP program PHPnuke. This product is often targeted by attackers to probe for XSS holes because of its popularity. I have included a few links of advisories/reports that have been discovered and disclosed just from this product alone. The following collection should provide plenty of examples.